Automatic downhole gas lift apparatus



J. K. ELLlOTT ETAL 3,415,199

AUTOMATIC DOWNHOLE GAS LIFT APPARATUS Dec. 10, 1968 8 Sheets-Sheet 1 Filed 001;. 13. 1966 m T mm Hu W mnw z mum I/ M M /M M M M w Q \4 Q m Y 5 M A T TORNE) 1953 J. K. ELLIOTT ETAL 3,415,199

AUTOMATIC DOWNHOLE GAS LIFT APPARATUS Filed Oct. 15, 1966 8 Sheets-Sheet 2 JAMES K. ELLIOTT (/05 550mm 5 JR. @0 Z INVENTO S ATTORNEY Dec. 10, 1968 J. K. ELLIOTT ETAL 3,415,199

AUTOMATIC DOWNHOLE GAS LIFT APPARATUS Filed Oct. 15, 1966 s Sheets-Sheet 5 A TZORNE) 10, 1958 J. K. ELLIOTT. ETAL 3,415,199

AUTOMATIC DOWNHOLE GAS LIFT APPARATUS Filed Oct. 13. 1966 8 Sheets-Sheet 4 [5 A. ELL/0T7 E EDWARDS JR. lN'VENTORS ATTORNEY 1953 J. K. ELLIOTT ETAL 3,415,199

AUTOMATIC DOWNHOLE GAS LIFT APPARATUS A TTORNEY Dec. 10, 1968 Filed Oct. 13, 1966 8 Sheets-Sheet 6 i "ij1 A T TORNE y J. K. ELLIOTT ETAL 3,415,199

AUTOMATIC DOWNHOLE GAS LIFT APPARATUS Dec. 10, 1968 8 Sheets-Sheet 7 Filed Oct. 13, 1966 WA DS JR T035 A TTORNE) Dec. 10, 1968 Filed Oct. 15. 1966 J. K. ELLIOTT EITAL AUTOMATIC DOWNHOLE GAS LIFT APPARATUS 8 Sheets-Sheet 8 DM/iW ATTORNEY United States Patent 3,415,199 AUTOMATIC DOWNHOLE GAS LIFT APPARATUS James K. Elliott and Joe E. Edwards, Jr., Houston, Tex.,

assignors to Macco Oil Tool Company, Inc., a corporation of Texas Filed Oct. 13, 1966, Ser. No. 586,468 6 Claims. (Cl. 103--248) ABSTRACT OF THE DISCLOSURE For use in oil wells produced by gas lift, apparatus including a chamber for accumulation of fluid from a producing formation, there being upper and lower float means in said chamber which control the admission of gas under pressure to said chamber when a suitable accumulation of liquid is attained therein for lifting same through a suitable tubing string to thereafter remove a predetermined quantity of liquid from said chamber.

The present invention relates to downhole gas lift apparatus, and more particularly relates to gas injection apparatus which accumulates liquids from a producing formation in a chamber with low back-pressure to obtain a predetermined and substantial volume whereupon gas is injected into the chamber to lift the liquid upwardly of the tubing string for recovery at the wellhead, it being noted that the apparatus functions sequentially automatically to deliver substantial volumes of liquid with each sequential operation.

One object of the present invention is to provide a new and improved gas lift valve for producing formations which utilizes a float in a closable chamber to sequentially gather liquid from the formation wherein the liquid accumulation and resultant movement of the float thereon initiates gas injection into the closed chamber wherein the liquid is lifted in the tubing string from the closed chamber, and the injection is automatically terminated on removing a substantial volume from the chamber.

A timely object of the present invention is to provide a new and improved gas lift valve apparatus which is float controlled to accumulate liquid prior to gas injection and subsequent lifting up the tubing string wherein the pressure injection first transfers a substantial portion of the liquid into the tubing string and then terminates operations automatically.

A related object of the present invention is to provide a new and improved gas lift apparatus which seals off the accumulation chamber during admission of high pressure gas to prevent forcing liquid back into the formation during lifting and wherein the chamber is maintained at a low back-pressure during liquid accumulation to permit accumulation of liquids as rapidly as possible from the producing formation.

A related object of the present invention is to provide a new and improved gas lifting apparatus including a closable chamber for delivering liquids into the tubing string wherein a surrounding annulus is provided for accumulating the continual production of the formation during delivery of the liquids trapped in the closable chamber.

Another object of the present invention is to provide a new and improved gas lift valve apparatus which vents gas diffused in the liquids to the casing annulus which is maintained at a low pressure during accumulation to-prevent the back-pressure from impeding the flow of liquids from the producing formation.

Yet another object of the present invention is to pro vide a new and improved gas lift valve apparatus which initiates and terminates the gas lifting cycle of operation on its own command which is preferably related to the 3,415,199 Patented Dec. 10, 1968 accumulation of a substantial and predetermined volume of liquid.

Yet another object of the present invention is to utilize a three-way valve communicating with a closable chamber for accumulation of liquids from a producing formation wherein the three-way valve either communicates the interior of the closable chamber with the casing annulus which is maintained at a low backapressure or the three-way valve injects gas under pressure into the closable chamber.

Other objects and advantages of the present invention will become more readily apparent from the consideration of the specifications and drawings wherein:

FIG. 1 is a sectional view of the gas lift valve apparatus of the present invention illustrating the initial condition of the invention;

FIG. 2 is a view similar to FIG. 1 illustrating an increase in liquid accumulation with three-way valve means exhausting or venting gas in the chamber into the casing annulus;

FIG. 3 is a view similar to FIG. 2 with the apparatus admitting gas under pressure into the closed chamber for lifting liquid in the tubing string:

FIG. 4 is a view similar to FIG. 3 partially illustrating completion of the step of lifting the liquid in the tubing string;

FIG. 5 is a sectional view of an additional embodiment of the present invention utilizing a float movable relative to a push rod connected with the valve means of the present invention;

FIG. 6 is similar to FIG. 5 but illustrates accumulation of liquid in the chamber to lift the float for injecting gas through the valve means of the present invention;

FIG. 7 is a sectional view of another alternative embodiment of the present invention similar to the structure shown in FIG. 1 provided with simplified valving; and

FIG. 8 is the embodiment shown in FIG. 7 illustrating accumulation of liquid in the chamber means to initiate gas injection.

Attention is first directed to FIG. 1 of the drawings which illustrates the preferred embodiment of the present invention. In FIG. 1, a well casing 10 is illustrated in sectional view and is intended to depict a casing extending through the earths surface and into a producing formation. Liquid from the formation is admitted to the interior of the well casing 10 by perforations or other apparatus (not shown) for accumulation of the liquid 12. A tubing string 14 for retrieving liquid from the means 16 of the present invention is located interiorly of a larger tubing string 15. The gas lift valve apparatus 16 of the present invention incorporates a closable chamber 18 for receiving the liquid 12 therein prior to injection of high pressure gas. A valve means indicated generally at 20 is provided with three ports, one of the ports communicating with the closable chamber 18, another port communicating with the casing annulus 22 and a third port com municating with the annulus 24 between the smaller tubing string 14 and the larger tubing 15. The present invention vents gas from the closable chamber 18 into the casing annulus 22 during accumulation of liquid to maintain minimum back-pressure while the valve 20 is closed to the annulus 24. Upon accumulation of sufficient liquid, the gas lift means 16 then operates valve 20 to inject gas under pressure from the tubing annulus 24 into the closable chamber 18 to lift the liquid 12 in the tubing string 14. Lifting of liquid from the closable chamber 18 continues until the liquid falls to a predetermined level in the chamber means 18, whereupon the valve 20 is closed off to the gas under pressure in the annulus 24. The pressure interiorly of the closable chamber 18 is vented and reduced to enable recycling of the present invention by additional liquid accumulation so that the device is self starting and self terminating and is adapted to function for an indefinite number of cycles when in stalled in a producing well.

Considering the invention more in detail, the sectional view of FIG. 1 illustrates the casing installed in the producing well. In the first instance, it should be noted that the relative width of the apparatus of FIG. 1 has been exaggerated to enable illustration of all details of the apparatus. The tubing strings 14 and 15 are preferably concentric of one another and are preferably concentric of the well casing 10 although the arrangement may be altered within the scope of the present invention. Tubing hangers are known in the art for positioning the tubing strings 14 and 15 in the casing 10. The tubing string 14 is provided with a conventional gas lift valve which is symbolically represented in the drawings of the present invention and which is intended to provide additional means for lifting the liquid to the wellhead in cooperation with the present invention as needed. Since gas lift valve 25 is only cooperative with the valve of the present invention and since it further does not relate to operations of the gas lift valve 16 of the present invention, it can be represented symbolically as shown in the drawings.

The tubing string 14 is somewhat longer than the tubing string 15, as shown in FIG. 1. The lower end of the tubing string 14, denoted as a tailpipe 26, extends almost to the lower end of the closable chamber 18, and is provided with an open end for receiving liquid therein. The opening of the tailpipe 26 is shaped at 26a to provide a valve seat for a standing valve including the spherical member 28. The standing valve 28 admits liquid to the tubing string 14 by pressure differential between pressure in the tubing string 14 and the chamber 18. The check valve 28 closes to reverse flow whereby a standing column of fluid .is maintained in the tubing string 1 The tubing string 15 suspends the present invention 16 from a threaded adaptor 30. The adaptor 30 is preferably a relatively large diameter circular member having an internally threaded shoulder for engaging the threads 31 at the lower end of the tubing string 15. The adaptor 30 extends inwardly of the tubing string 15 to cap otf the lower end of the tubing 15 and seal off the tubing string 15. A seal member 32 of conventional material is located at the central opening of the adaptor 3:0 as a pressure seal to maintaining a leakproof connection between the adaptor 30 and the tubing string 14.

The outer edge of the adaptor 30 is threaded for connection to a cylindrical member 34 which defines the chambermeans 18 proper. Cylindrical member 34 is threaded at 34a for joinder to the adaptor 30. In addition, a seal member 36 is received in a groove 30a facing the internal surface of the means 34 for sealing the threaded connection of the cylindrical member 34 and the adaptor 30.

The lower end of the closable chamber means 18 is of unitary construction as indicated at 341). The lower closure member 34]) has a centrally located opening 34c which extends upwardly to a valve seat 34d receiving a valve member 38 whereby liquid flow from the closable chamber 18 is prevented. As shown in FIG. 1, the inflow of liquid accumulated in the casing 10 opens the standing valve 38 to maintain an equal head of liquid in the chamber means 18. As will'be discussed with reference to FIGS. 2 and 3 and 4, the valve 38 prevents reverse flow from chamber 18 on injection of gas under high pressure which forces the liquid inwardly in the tubing string 14 through the valve 28.

As previously noted, the large tubing string 15 conveys gas under pressure to the gas lift means 16 of the present invention. By way of example, the pressure in the large tubing 15 can be in the range of 400-1080 psi. The casing annulus 22 is preferably maintained at a relatively low pressure to provide a minimum back-pressure as will be noted. By way of example, the casing annulus 22 can be essentially open so that the back-pressure acting on the means 16 is not significant.

Three-way valve means 20 are supported from the lower face of the adaptor 30. The valve means 20 is preferably a spool valve including a central port 40 opening into the chamber means 18. Additional ports of the valve 20 include a chamber venting port 42, it being noted that the port extends through the adaptor 30 by means of appropriate tubing or the like. Likewise, the valve port 44 communicates gas under pressure in the annulus 24 with the chamber 18 through a conduit extending through the adaptor 30. It will be noted that the spool of the valve 20 is arranged to enable fluid flow between either port 42 or 44 with the chamber port 40.

The tailpipe 26 is utilized in the preferred embodiment to support an upper control valve 48. Control valve 48, mounted on an appropriate bracket 50, is preferably a spring return, push rod operated spool valve with connections to the three-way valve means 20 as will be described.

In addition, the support member 50, which is joined to the tailpipe 26, includes a pivot arm 52 which is connected with a ring-shaped float means 54. The float 54 encircles the tailpipe 26 which is a means of guidance and direction to movements of the float 54. The float 54 responds to the rising level of liquid 12 in the chamber means 18 whereby the float is moved upwardly from the canted position shown in FIG. 1 to operate the control valve 48. This will be described in greater detail when discussing the present invention.

The float 54 is joined by way of a tab with the push rod of the spool valve 48 for movement of the spool. As shown in FIG. 1, full extension of the push rod to its limit is associated with the closed condition of the valve 48.

An additional control valve 56 is also suspended at a predetermined level in the chamber means 18 by an appropriate support member 58 joined to the tailpipe 26 by welding or other appropriate means. The valve 56 is similar to the valve 48 and is a spring return, push rod operated spool valve which is actuated by a float means 60. Float means 60 is a hollow, ring-shaped member having a protruding tab or ear pivotally joined with a pivot mounting arm 62 carried on the lower side of the support member 58. In addition, an eyelet connector is provided for connection to the push rod of the spool valve 56, it being noted that the arrangement of the pivot and the push rod of the spool valve communicate upward movement of the float means 60 to the spool for controlling fluid flow through the valve 56. It should be noted generally that the spool valve 56 and associated float 68 are similar or even identical to the apparatus 48 and 54 above noted. The float 54 is joined by way of a tab with the push rod of the spool valve 48 for movement of the spool. As shown in FIG. 1, full extension of the push rod to its limit is associated with the closed condition of the valve 48. As shown in FIG. 1, full extension of the push rod to its limit is associated with the open condition of the valve 56.

A significant difference in the two control valves and floats is the relative location in the chamber 18. In this regard, the subsequent discussion of the relationship of the location of the floats 54 and 60 will show the present invention pumps a predetermined volume of liquid up the tubing string 14. Pressure fluid for valve means 20 regulated by the control valves 48 and 56 is taken from the large tubing annulus 24 by means of a feed-through pipe 78. The tubing 70 has a branch 72 which communicates with the valve 48 which, when open, continues flow from the conduit 72 into the conduit 74. In addition, conduit 70 also communicates fluid to a branch 76 extending to control valve 56 which. when open, continues fluid flow to a control conduit 78. Control tubing 78 continues to the left hand end of the valve means 20 to move the spool of the valve to a position determined by fluid flow in the control line 78.

An exhaust system is also provided through the control valves 48 and 56 for pressure from the spool valve when the spool is moved to the opposite end of the valve chamber. Specifically, an exhaust line 80 communicates through the adaptor and into the casing annulus 22 for venting pressure fluid from the low pressure side of the valve means 20. Exhaust line 80 includes a branch 82 which communicates through the control valve 48, which, when open, communicates by way of an additional line 84 to the previously noted conduit 78. In addition, a branch line 86 exhausts pressure fluid through the valve 56 which, when open, communicates the line 86 with an additional conduit 88. Conduit 88 is connected with the previously noted conduit 74.

The control valves 48 and 56 both provide control pressure to the valve means 20 and an exhaust route from the opposite end of the valve 20 to permit the valve spool in the valve 20 to move freely against minimum backpressure. Byway of example, the illustrated position of the valves shown in FIG. 1 communicates fluid under pressure through the line 76, control valve 56, line 78 and into the left hand end of the valve means 20. Movement of the spool from the left hand end towards the right hand end expels gas through the conduit 74, conduit 88, control valve 56, branch 86 and exhaust line 80 into the casing annulus 22. Flow of the pressure through the inlet conduit 70 and the exhausting of pressure fluid through the line 80 is indicated in FIG. 1 by the arrows interposed on the fluid lines.

The sequence of operations in the gas lift valve 16 of the present invention is illustrated in FIGS. 1 through 4, inclusive. The sequential illustrations show the initial filling of the chamber means 18 wherein the liquid 12 flows through the standing valve 38. The liquid level of FIG. 1 should be contrasted with the level shown in FIG. 2 wherein the float 60 has been lifted by its bouyancy to operate the control valve 56. Specifically, the spool of the valve 56 terminates flow through the control line 76 to the valve means 20. It having been previously noted that flow through the lines 76 and 78 moves the spool of the valve means 20 to the right, the interruption of flow through the inlet lines 76 maintains the valve spool in the last position. Also, the exhaust route through conduits 86 and 88 is interrupted whereby the valve means 20 is maintained in the initially provided position.

FIG. 2 illustrates operation of the valve means 20 to vent gas from the chamber means 18. Liquid accumulation in the chamber means 18 drives gas from the chamber through the port and outwardly through port 42 into the casing annulus 22. Moreover, the liquid itself is susceptible to surrender of diffused gas which further tends to increase the pressure in the chamber means 18. Therefore, as a means of venting excessive back-pressure, the vent means is provided communicating the chamber means 18 with the casing annulus 22 whereby rapid liquid accumulation is materially expedited. As represented by the arrow in FIG. 2, gas is vented through the port means 40 and the tubing 42.

It will be appreciated that the accumulation of liquid indicated in FIG. 2 fully submerges the float 60 and buoys upwardly the float means 54. This is shown in FIG. 3 wherein the liquid 12 is accumulated to the level of the float 54. As the float 54 is carried upwardly on the surface of the liquid, it pivots on the pivot arm 52 and moves the push rod connected with the spool of the valve 48 upwardly. Upward movement of the spool opens passages of communications through the valve 48 wherein the pressure in line 72 is communicated to the line 74 and the pressure exhaust line 84 is communicated with the line 82. The flow arrows of FIG. 3 represent fluid flow from the pressure inlet line 70 through the valve 48 and into the right hand end of the valve 20 resulting in movement of the spool to the left. Leftward movement of the spool expels fluid from the left hand end of the valve 20 through the conduit 84 and outwardly to the vent line 80. Movement of the spool to the left hand end of the valve 20 communicates the chamber port 40 with the gas injection port 44. Admission of gas under high pressure to the chamber means 18 on opening the control valve 48 initiates lifting of liquid from the chamber means 18 whereby liquid is forced into the upstanding tubing string 14.

It will be appreciated that the process of lifting liquid from the chamber means 18 and upwardly of the tubing string 14 is dependent on continued admission of gas under pressure from the tubing annulus 24. In this regard, attention is referred to FIG. 4 which illustrates partial completion of lifting of liquid from the chamber means 18. It will be noted that the liquid level illustrated in FIG. 4 is below the level of the float member 54 whereby the float has dropped downwardly to a condition similar to that shown in FIG. 1. Downward movement of the float 54 closes the valve 48. It will ibe noted further that both control valves 48 and 56 are closed to prevent any fluid flow in the control lines to sustain the valve means 20 in the illustrated condition. As the liquid level drops below the valve 48 and its associated float 54 and the valve 48 is closed by the float, valve means 20 continues to inject gas into the chamber means 18 without interruption whereby the liquid in the chamber means 18 is expelled upwardly of the tubing string 14. This is the condition illustrated in FIG. 4 and it will be appreciated that the liquid level drops from that illustrated in FIG. 3 to a point lowering the float 60 in the chamber to reopen control valve 56. This completes one cycle of operation of the gas lift apparatus of the present invention.

It should be noted that in the transfer of liquid from the chamber means 18 through the standing valve 28 and into the tubing string 14 that the devicerepetitively delivers approximately the same volume with each operation. Moreover, the flow of liquid in the tubing string 14 to the conventional gas lift valve 25 enables final recovery of the liquid and delivery to the wellhead.

Attention is next directed to FIGS. 5 and 6 which illustrate an alternative embodiment of the present invention indicated by the numeral 116. The structure shown in FIG. 5 is incorporated with a casing string 110 which surrounds a smaller tubing string 114 placed within a slightly larger tubing string 115. The casing string 110 encloses a casing annulus 122 while a smaller annulus 124 is provided through which gas under pressure is communicated. Typically, gas in the range of 400 to 1,000 psi. can be provided for operation of the device of the present invention.

The gas lirft appanatus 116 of the present invention is somewhat similar to the structure shown in FIG. 1 and to this extent, similar components bear reference numerals increased by 100. Thus, it will be noted that the adaptor plate is joined to the cylindrical member 134 which includes a bottom member 13419 for defining the chamber means 118. In addition, a standing valve 138 is provided in the lower portions of the chamber means 118 for admitting liquid to the chamber from the producing formation. Likewise, a tailpipe 126, an extension of the small tubing string 114. includes a standing valve 128 for admitting liquid from the chamber means into the tailpipe 126. Other similarities will be noted from an examination of FIGS. 5 and 6 and the previously described views.

Of particular interest to the structure shown in FIG. 5 is the valve means 120 which is operated by movements of a connective rod as opposed to the operation of the valve 20 (see FIG. 1) which is opened and closed by control valves 48 and 56. The float member 154 is provided with a walled opening through the buoyant structure of the float whereby the control rod 150 restricts the motion of the float member 154. A gusset 1261) is welded to the exterior of the tailpipe and has an upwardly facing hole or guide for receiving the lower end 150a of the control rod. In addition, an enlargement 15012 is located on the control rod 150 near the lower end and a similar enlargement 150e is carried on the control rod immediately below the valve means 120.

The upward and downward movements of the float 154 borne on the surface of the liquid 112 carry the float to the extremes of movement permitted by the enlargements 15012 and 150e. On the downward movement of the float 154, the enlargement 15017 is engaged as shown in FIG. whereby the control rod 150 is moved downwardly against the resilient member 153. The downward movement of the control rod 150 moves the spool in the valve means 120 to provide a fluid path of communications including the chamber port 140 of the means 120 and the outlet port 142 communicating with the casing annulus 122. It was previously noted that the casing is maintained at a relatively low pressure whereby gas under pressure is vented from the chamber means 118 into the casing annulus 122 against minimum back-pressure. As previously noted, the port 144 provides an inlet from the annulus 124 through the valve means 120 into the chamber means 118 to inject gas under pressure. As has been previously noted, the liquid 112 accumulated in the chamber means sometimes carries dissolved gas which tends to bubble off at reduced pressures to fill the chamber with gas. Also, the addition of liquid to the chamber means 118 requires the exhaustion of air from the chamber. It should be further noted that the liquid 112 is admitted to the chamber means 118 through the standing valve 138. The accumulation of liquid lifts the float 154 upwardly along the control rod 150 without changing the position of the valve means 120 since the valve means 120 and the control rod are sufficiently inert to maintain the control rod in the last attained position until the float means 154 engages one of the enlargements.

FIG. 6 illustrates the float means 154 lifted by the liquid 112 to contact the enlargement 150a on the control rod 150. The movement of the control rod upwardly moves the spool in the valve means 120 whereby fluid flow through the valve means is altered. Specifically, the arrows in FIG. 6 indicate the flow of gas under pressure from the tubing annulus 124 through the port 144 and the chamber port 140. Since the chamber means 118 is a closable chamber by operation of the standing valve 138, the admission of gas under high pressure lifts the liquid from the chamber means 118 in the tubing string 114. The standing valve 128 in the tubing string is shown in the open position whereby the liquid flows upwardly into the tubing string 114. The liquid is evacuated from the charm ber means 118 by gas injection until the float member 154 is moved from the position shown in FIG. 6 at an upper, predetermined level in the chamber means to a lower level (see FIG. 5). At this point, the valve member 120 is reoperated to return the valve to the condition previously shown in FIG. 5. Thereupon, the apparatus can recycle to deliver another volume of liquid.

Attention is next directed to FIGS. 7 and 8 which illustrate a third alternative embodiment of the present invention indicated by the numeral 216. The structures shown in FIGS. 7 and 8 are arranged in similar installations to those previously shown. For instance, the well casing 210 surrounds the chamber means 218 carried below the adaptor 230 which is connected to the tubing strings 214 and 215. Other portions of the structure are identified by the numerals found in FIG. 1 increased by 200.

The structure 216 uses control valves 24% and 256 which are similar in function and arrangement to the valves 48 and 56 shown in FIGS. 1 through 4 inclusive. The provision of pressure fluid to the valves 248 and 256 for operation of the valve means 220 is distinctive as will be noted hereinbelow. The injection gas provided in the tubing annulus 224 is communicated through the conduit 270 to either of the valves 248 or 256 through branches 272 or 276. The valves communicate with branches 274 and 278 connected to opposite ends of the valve means 200. The valve means 220 is similar to the valve means 20 in providing a spool operated, three-way valve which has a chamber port 240, a vent port 242 and a port 244 communicating with gas under pressure in the tubing annulus 224. However, the distinctions of the structure shown in FIGS 7 and 8 lie, in part, in the provision of bleed chokes 220a and 22%. The bleed choke 220a is communicated with the right hand end of the spool valve by the conduit 274a and the restricted flow of gas then passes through the branch 242a to the vent line 242. Likewise, conduit 278a flows pressure fluid through the choke 22% which connects with the branch line 242k and thence to the vent line 242.

In operation of the valve 220, it will be recognized that the illustrated position in FIG. 7 is achieved by admitting gas under pressure through the gas line 278 into the left hand end of the valve means 220. Gas is expelled from the right hand end by movement of the spool. The fluid line is exhausted through the branch 274a to the choke 220a and is eventually vented through the line 242. It will be appreciated that the fiow of gas into the left hand end of the valve means 220 is accompanied by a continual leakage through the choke 22% and the vent means 242. However, in view of the large volume of gas provided under pressure in the tubing annulus 224, the small leakage through the bleed choke is no burden to the gas injection system.

Considering the embodiment 216 as a whole, the structure is similar to the embodiment 16 previously discussed. Specifically, the control valves 248 and 256 are operated by the float members 254 and 260, respectively. The lower float 269 opens control valve 256 to provide control pressure to the valve means 220 for positioning the spool at the right hand end of the valve as illustrated in FIG. 7. When the liquid rises to the level of the float 260 and closes the valve 256, the absence of flow through conduit or line 278 leaves the spool of the valve in the condition previously attained. This provides a vent for gas in the chamber means 218 into the casing annulus 222. This is similar to the process described for the embodiment 16.

The accumulation of liquid in the chamber means 218 to the level of the float 254 is illustrated in FIG. 8. The buoyant float 254 is lifted to open the valve 248, and control fluid is admitted through the line 272 into line 274 for moving the spool of the valve means 220 to the left hand end. Movement of the spool admits gas from the tubing annulus 224 through the port 244 and the port 240 into the chamber 218. Injection of gas under pressure drives the liquid from the chamber means 218 upwardly through the tailpipe 226 whereby the liquid is lifted in the small tubing string 214 towards the wellhead. As the liquid level drops in the chamber means 218, the valve 248 is eventually closed as the float memher 254 drops to its original position but the valve 220 is maintained in the illustrated position of FIG. 8 until the valve 256 is opened. Thereupon, the cycle of operation is repeated wherein the liquid is again accumulated to the level illustrated in FIG. 8. As a consequence of the above sequence, the gas lift valve means 216 of the present invention cycles to repetitively deliver liquid through the tubing string 214.

It should be noted that the standing valve 238 closes when gas under pressure is admitted to the chamber means 218. This is particularly advantageous when using the gas lift apparatus 216 with producing formations with low internal pressures or inadequate formation drive against high back-pressure. Moreover, the devices of the present invention are adapted for use with conventional gas lift valves as previously noted where the additional gas lift valves are used to complete lifting of the liquid to the wellhead.

The description of the above noted embodiments is directed to three embodiments of the present invention;

9 however, the scope of the present invention is to be determined by the appended claims.

What is claimed is:

1. A device for lifting liquid in a well using gas under pressure supplied through a first tubing string comprising:

(a) chamber means adapted to be connected to a second tubing string for accumulating liquid therein from a formation;

(b) three-way valve means communicating said chamber means with the first tubing string for admitting gas under pressure to said chamber means;

(c) said valve means alternately communicating said chamber means with the well string maintained at a relatively low back-pressure for relieving pressure in said chamber means on accumulation of liquid there- 1n;

(d) a first valve means;

(e) a second valve means;

(f) supply line means providing gas under pressure to each of said first and second valve means;

(g) conduit means extending from said first valve means to said three-way valve means to operate same to vent gas in said chamber means into the well string;

(h) additional conduit means extending from said second valve means to said three-way valve means for operating said three-way valve means to admit gas under pressure to said chamber means for lifting liquid in said chamber means in the second tubing string;

(i) float means opening said first valve means to supply .gas through said supply line means and said conduit means to operate said three-way valve means to vent gas in said chamber means into the well string;

(j) additional float means opening said second valve means to supply gas through said supply line means and said additional conduit means to operate said three-way valve means to admit gas under pressure to said chamber means for lifting liquid in said chamber means in the second tubing string; and

(k) said additional float means being located in said chamber means above said float means to define the volume of liquid lifted from said chamber means.

2. The apparatus of claim 1 wherein said three-way valve means is a spool valve.

3. The apparatus of claim 2 wherein gas under pressure is applied to one end of said spool valve, and an additional conduit means extends from the opposite end thereof to one of said valve means for exhausting gas from the opposite end of said spool valve.

4. The apparatus of claim 2 wherein bleed port means are communicated with both ends of said spool valve and the well string for exhausting gas from said spool valve.

5. A device for lifting liquid up a tubing string in a well with gas under pressure supplied to the device, comprising:

(a) a chamber means for accumulating liquid in the well from a formation, said means including a connection with a tubing string in the well;

(b) first valve means having two positions, one being an open position for communicating gas under pressure supplied through the well string with said chamber means to lift liquid from said chamber means and up the tubing string;

(c) said first valve means having a closed position preventing admission of gas under pressure to said chamber means to permit accumulation of liquid in said chamber means at reduced pressures therein;

((1) a first float means located at a lower level in said chamber means;

(e) a second valve means operated by said first float means for communicating control pressure fluid to said first valve means for maintaining same in a posi- 10 tion closing said chamber means to gas under pressure;

(f) upper float means located at the predetermined level in said chamber means;

(g) third valve means operated by said upper float means for communicating control pressure fluid to said first valve means for maintaining same in a position admitting gas under pressure to said chamber for lifting liquid from said chamber means; and,

(h) said lower and upper float means responding to liquid level in said chamber means and operating said second and third valve means, respectively, to open said first valve means for admitting gas under pressure to said chamber means on accumulation of liquid to said upper float means, and also closing said first valve means after the gas under pressure has lifted liquid from said chamber means to act on said lower float means.

6. A device for lifting liquid upa tubing string in a well with gas under pressure supplied to the device, comprising:

(a) a chamber means for accumulating liquid in the well from a formation, said means including a connection with a tulbing string in the well;

(b) first valve means having two positions, one being an open position for communicating gas under pressure supplied through the well string with said chamber means to lift liquid from said chamber means and up the tubing string;

(c) said first valve means having a closed position preventing admission of gas under pressure to said chamber means to permit accumulation of liquid in said chamber means at reduced pressures therein;

(d) a first float means located at a lower level in said chamber means;

(e) a second valve means operated by said first float means for communicating control pressure fluid to said first valve means for maintaining same in a position venting said chamber means into the well string to permit liquid to accumulate therein against reduced back pressure;

(f) second float means located at the predetermined level in said chamber means;

(g) third valve means operated by said second float means for communicating control pressure fluid to said first valve means for maintaining same in a position closing said chamber means to communication with the well string; and,

(h) said lower and upper float means responding to liquid level in said chamber means and operating said second and third valve means, respectively, to open said first valve means for admitting gas under pressure to said chamber means on accumulation of liquid to said upper float means, and also closing said first valve means after the gas under pressure has lifted liquid from said chamber means to act on said lower float means.

References Cited UNITED STATES PATENTS 122,332 1/1872 Roe 103-248 2,177,517 10/1939 Cuthrell 103-248 X 2,207,318 7/1940 Gollner 103234 X 2,223,417 12/1940 Havens 103248 2,730,961 1/1956 Yeomans 103248 X 2,764,104 9/1956 Yeomans 103248 3,302,586 2/1967 Brugnoli 103232 FRED C. MATTERN, JR., Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

U.S. Cl. X.R. 103232 

